As for the substrates for adhesive sheets, resin films produced by polymerizing and curing photopolymerizable urethane acrylate oligomers have been used. Urethane acrylate oligomers are obtained by reacting a polyether polyol or polyester polyol compound and a polyisocyanate compound, as described in Patent Literature 1 (Japanese Patent No. 3739570). With respect to urethane acrylate oligomers from a polyester polyol compound, Patent Literature 2 (Japanese Patent No. 3177149) describes urethane acrylate oligomers that have structural units derived from polyester diol.
However, materials for the production of urethane acrylate oligomers having structural units from polyester diol are limited in variety and tend to be expensive. Urethane acrylate oligomers having structural units from polyether diol cause problems when cured resin films thereof are used in semiconductor-processing sheets such as surface protective tapes, dicing tapes and die-bonding tapes. In detail, because the semiconductor processing sometimes involves high temperatures, the weight of substrates reduce as a result of the outgassing through heat decomposing and are deteriorated to fail to achieve expected performance. Further, the outgassing fail to contaminate surrounding devices and the like.